Steel String Singer #005 build

[captaincoconut]

Thanks, Martin! I'll post a schematic and layout of my build when everything is finished.

[captaincoconut]

Found this quote from EJ in a Guitar Player interview from 1986: "The second system is for dirty rhythm. It has a Howard Dumble Steel String Singer, a real powerful amp, going through a Marshall 4x12 box wired for 8 ohms. The Dumble has two different types of built-in gain boosts - a tone-defeat circuit and an active FET preamp - so it has three different overdrive sounds. I turn the amp's preamp up and set the master volume between 5 and 7, depending on how big the hall is. I usually use the amp's deep switch - this gives it a real nice low, tight bass sound - and bright switch to get a nice panorama of EQ with good lows and highs. The other controls are set about halfway up. I use the Dumble with an Ibanez Tube Screamer and an MXR Digital Delay."

[captaincoconut]

Do you guys have any input on how much of a tonal influence the two coupling caps between the phase inverter and cathode follower have? Everybody seems to agree that #005 uses standard Marshall values for the phase inverter (470R/10k) but I see different choices for the coupling caps after the phase inverter. Builders like Amplified Nation seem to use 22nF (= Marshall value), Beasley used 47nF in his build. Is there a noticeable difference between those values?

[markusw]

I can't imagine that it will have a noticeable impact as the high pass filter cutoff shifts from ~ 7 Hz to 15 Hz (edit: 47n to 22n).
Well below the guitar frequency range.

[captaincoconut]

I can't imagine that it will have a noticeable impact as the high pass filter cutoff shifts from ~ 7 Hz to 15 Hz (edit: 47n to 22n).
Well below the guitar frequency range.

That's what I figured, but always wondering about those choices. Thanks!

[Roe]

I can't imagine that it will have a noticeable impact as the high pass filter cutoff shifts from ~ 7 Hz to 15 Hz (edit: 47n to 22n).
Well below the guitar frequency range.

It affects blocking distortion and recovery speed more than bass response. The lower values give a faster response with tighter bass. Even 15nf works well (w. 220k bias splitters).

[markusw]

It affects blocking distortion and recovery speed more than bass response. The lower values give a faster response with tighter bass. Even 15nf works well (w. 220k bias splitters).

Good to know

[captaincoconut]

Yep, thanks

[Roe]

It affects blocking distortion and recovery speed more than bass response. The lower values give a faster response with tighter bass. Even 15nf works well (w. 220k bias splitters).

Good to know

many of the standard values are unnecessarily large (e.g. 100nf) and contributes to flubby bass and a slow response at full power (sometimes it even contributes to ghosting and sag). Marshall superbasses and JTMs, for example, have soo much low bass that many keep the bass knob on 0-1 and still recording techs tend to use a bass cut (high pass filter) at 80-120hz (many techs even add a bass cut on superleads with 22nf caps). One you remove some low bass, you get a faster response which is more focused and powerful (like a trainwreck). But this is mainly a major issue when the amp distorts and you run into blocking distortion.

Another solution is adding grid resistors (but watch the max grid leak resistance)

[captaincoconut]

I haven't really worked on this amp for about a month, but I'm starting to see the end. I will post some updates soon!

[ijedouglas]

Dream work station! Very nice!

[Guy77]

I haven't really worked on this amp for about a month, but I'm starting to see the end. I will post some updates soon!

Your amp looks beautiful! Especially your faceplates!!!

I was curious were they made with anodized aluminum?
Also what brand of caps did you use for the High Filter?


Congrats!
Guy

[captaincoconut]

Your amp looks beautiful! Especially your faceplates!!!

I was curious were they made with anodized aluminum?
Also what brand of caps did you use for the High Filter?


Congrats!
Guy

Thanks guys! The faceplates are indeed anodized aluminium with UV print. Really well made but not cheap!

I used Mica caps for the High Filter. It's a mixture of Tube Town, Tube Amp Doctor and Cornell Dubilier branded Mica caps as I couldn't get all the values from the same supplier. I GUESS they are all made by Cornell Dubilier, though.

[captaincoconut]

Guys, is this correct for the FET boost? Voltage divider is 150k/8.2k, source resistor is a trimpot set up as a variable resistor. Going for the lower headroom bias I used a 9.0V power supply and set drain voltage to 3.0V (Vdd/Vd = 3.0 according to Martin's instructions).

[martin manning]

That should be good to go. When you install it in the amp and hook up the B+ the ratio Vdd/Vd should drop to ~2.2 or 2.3.